This invention relates to an adjustable pipe extender for high pressure pumping lines for pumping of abrasive materials and particulary concrete and the like.
The concrete pumping industry has developed a standard length pipe section for the assembly of concrete pumping distribution lines. Such pipe sections are formed with the necessary formed end shoulders defining outwardly projecting members for interconnection with standard releasable couplings. Concrete pumping is a very high pressure environment. Pressures of two to three thousand PSI and even higher transient pressures may be encountered. Concrete pumping is also a very harsh environment. The system operates in an environment including airborne foreign matter and the concrete itself is a very abrasive and damaging material. The couplings must therefore be designed to operate as high pressure couplings which can be opened and closed with the desired firm interconnection of the pipe in the presence of concrete and other foreign matter.
In the construction of concrete pumping apparatus and systems, various fixed connecting locations are encountered. Although the apparatus and system design is perferably made to accommodate standard lengths of pipe used in concrete pumping line, small variations in the connection locations are often encountered. Generally, minimal sized variations have been accomodated by the use of shimms located within the joint structures. However, larger variations in the distance between coupling locations require custom built connectors. Further, shimms and like coupling modification often result in a faulty connection. For example, closing of the clamp assembly on the shimmed pipe end may prevent establishing a complete closure with the necessary firm reliable connection to hold transient pressures. A less than fully closed clamp connection is subject to opening and particularly in the presence of high transient pressures such as encountered in concrete pumping systems. Further, such connections may tend to allow undesirable leaking of the pumped concrete.
A practical application in automated concrete pumping systems is encountered in a mobile pump unit provided with an adjustable boom structure for distributing of the concrete within an expanded area adjacent the location of the mobile unit. Mobile pumping units for example are shown in U.S. Pat. No. 3,860,175 which issued on Jan. 14, 1975 and U.S. Pat. No. 3,918,749 which issued Nov. 11, 1975. Mobile units generally include various connecting pipes including vertical and horizontal disposed pipes connecting a supply hopper to a concrete distribution line. An extendable multi-section boom structure is mounted for extension of the pipe line system and particularly the discharge pipe at the drop location within specific distances of the mobile unit. The vertical and horizontal pipes are interconnected with appropriately located coupling units to permit location and orientation of the boom for proper location of the discharge end of the pipe.
In the construction of mobile boom mounted pumping systems, various collapsible folding boom designs are used including folding boom sections for supporting of the pipe line. Generally, fixed pipe elbows interconnecting are provided at the pivot points of the boom structure to couple the pipe sections on the adjacent boom sections. Such pivot points are of course fixed by the boom design. In the design of such systems, variation in the location of the several interconnecting pipe line swivel joints and couplings which are fixed by the boom construction often occur. Further, manufacturing tolerances often may require adjustment or compensation to adjust for the particular location of the joint and coupling. The manufacturers of such equipment prefers use of standard pipe sections, but other design requirements may demand use of special pipe to accommodate variations in the coupling locations.
For example, concrete pumping pipe sections normally are of a fixed length and typically in the United States are formed as 10 foot pipe. The distance between fixed points in a line may not be that accurately formed. Thus, in construction of boom-mounted pumping lines, the manufacturing tolerances and differences in construction of different models may result in significant variation in the necessary pipe length required to complete the pumping line. Rather than custom building a special section, the builder will, if possible, use shimms to compensate for any variation between the standard 10 foot lengths of pipe. If shimms cannot be used, a special pipe section is built for each truck. Replacement of course is difficult because each truck may require a special length. A further similar application is encountered in pumping of concrete in high rise structures. In construction of high rise structures such as buildings and other high rise structures, the concrete may be conveniently pumped to a vertical level and then laterally through the distribution pipe line portion. In such systems, a vertically oriented pipe line system is assembled on site by interconnecting of pipe sections. The pipe sections are mounted in stack relation and interconnected with suitable quick release couplings as needed to reach a particular level, with additions of vertical sections as needed. The tolerances in the building structures may result in a variance of a couple of inches at any given floor and require use of a special pipe length to properly locate the horizontal distribution line. In such systems, it is also often necessary to clean out the lines, which may require removal of one pipe section. If a lower one of a plurality of vertically oriented pipe sections is removed, the total line may shift downwardly a very sight amount. Any such variance however will make it extremely difficult, if not impossible, to reinsert the removed pipe section. To modify and build a custom pipe section would not only delay the process but would be extremely costly. An adjustable pipe section is therefore highly desirable in such an application.
In summary, the use of shimms and the like reduce the effectiveness of the coupling of the connections. In such constructions, leakage may occur and difficulty in movement of the connection may also be encountered.
The difficulty and problems associated with the providing of a high quality and reliable line connection has created a demand for an adjustable pipe section which can be readily used at minimal cost.